2 Intermolecular Forces Intermolecular Forces: weaker interactions that occur between molecules. These are collectively known as Van der Waals forces.Intramolecular Forces: Do not confuse Inter with Intra! Intramolecular forces are how we describe bonding between atoms.
15 Types of Solids: Metals The electron sea model for metals postulates a regular array of cations in a "sea" of valence electrons. (a) Representation of an alkali metal (Group 1A) with one valence electron. (b) Representation of an alkaline earth metal (Group 2A) with two valence electrons.
16 Types of Solids: Metals Alloy: A substance that contains a mixture of elements and has metallic propertiesSubstitutional Alloy (a): some of the host metal atoms are replaced with atoms similar size metal atomInterstial Alloy (b): some of holes between the metal atoms are filled with smaller atoms
25 Heating Curves Temperature Change change in KE (molecular motion) depends on heat capacityHeat Capacityenergy required to raise the temp of 1 gram of a substance by 1°C-
26 Heating Curves Phase Change change in PE (molecular arrangement) temp remains constantHeat of Fusion (Hfus)energy required to melt 1 gram of a substance at its m.p.
27 Heating Curves Heat of Vaporization (Hvap) energy required to boil 1 gram of a substance at its b.p.usually larger than Hfus…why?EX: sweating, steam burns, the drinking bird
28 Phase DiagramsWe know that different compounds can have different phases.These phases depend on the temperature and pressure of the substance.TemperaturePressureWe can then use that information to create a diagram of the different phases called a PHASE DIAGRAM.
29 Looking at Phase Diagrams The boundaries between phases occur at phase changes (ie. melting, freezing, vaporizing, etc.)SLGTemperaturePressureA - melting, freezingABB - vaporization, condensationC - sublimation, depositionC
30 Looking at Phase Diagrams The triple point is where the boundaries converge at one point and all three phases are present at the same time.SLGTemperaturePressureTriple Point
31 Looking at Phase Diagrams The critical point is the point at which the distinction between the liquid phase and gas phase ceases to exist.SLGTemperaturePressureCritical Point
32 Determining the Melting Point Find the current pressureDraw a line across the diagramAt the boundary between the solid and liquid phase, draw a line down to the temperatureDetermine the temperatureSLGTemperaturePressure1 atm
34 Phase DiagramsEach substance or compound has different melting/freezing points, boiling/condensing points, and sublimation/deposition points.Therefore, each substance or compound has a different phase diagram.Carbon